/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the  "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id$
 */
package wx.xml.xalan.xml.dtm.ref;

import wx.xml.xalan.xml.dtm.DTMAxisIterator;

/**
 * This class serves as a default base for implementations of mutable
 * DTMAxisIterators.
 */
public abstract class DTMAxisIteratorBase implements DTMAxisIterator {

    /**
     * The position of the last node within the iteration, as defined by XPath.
     * Note that this is _not_ the node's handle within the DTM. Also, don't
     * confuse it with the current (most recently returned) position.
     */
    protected int _last = -1;

    /**
     * The position of the current node within the iteration, as defined by XPath.
     * Note that this is _not_ the node's handle within the DTM!
     */
    protected int _position = 0;

    /**
     * The position of the marked node within the iteration;
     * a saved itaration state that we may want to come back to.
     * Note that only one mark is maintained; there is no stack.
     */
    protected int _markedNode;

    /**
     * The handle to the start, or root, of the iteration.
     * Set this to END to construct an empty iterator.
     */
    protected int _startNode = DTMAxisIterator.END;

    /**
     * True if the start node should be considered part of the iteration.
     * False will cause it to be skipped.
     */
    protected boolean _includeSelf = false;

    /**
     * True if this iteration can be restarted. False otherwise (eg, if
     * we are iterating over a stream that can not be re-scanned, or if
     * the iterator was produced by cloning another iterator.)
     */
    protected boolean _isRestartable = true;

    /**
     * Get start to END should 'close' the iterator,
     * i.e. subsequent call to next() should return END.
     *
     * @return The root node of the iteration.
     */
    public int getStartNode() {
        return _startNode;
    }

    /**
     * @return A DTMAxisIterator which has been reset to the start node,
     * which may or may not be the same as this iterator.
     */
    public DTMAxisIterator reset() {

        final boolean temp = _isRestartable;

        _isRestartable = true;

        setStartNode(_startNode);

        _isRestartable = temp;

        return this;
    }

    /**
     * Set the flag to include the start node in the iteration.
     *
     * @return This default method returns just returns this DTMAxisIterator,
     * after setting the flag.
     * (Returning "this" permits C++-style chaining of
     * method calls into a single expression.)
     */
    public DTMAxisIterator includeSelf() {

        _includeSelf = true;

        return this;
    }

    /**
     * Returns the position of the last node within the iteration, as
     * defined by XPath.  In a forward iterator, I believe this equals the number of nodes which this
     * iterator will yield. In a reverse iterator, I believe it should return
     * 1 (since the "last" is the first produced.)
     * <p>
     * This may be an expensive operation when called the first time, since
     * it may have to iterate through a large part of the document to produce
     * its answer.
     *
     * @return The number of nodes in this iterator (forward) or 1 (reverse).
     */
    public int getLast() {

        if (_last == -1)        // Not previously established
        {
            // Note that we're doing both setMark() -- which saves _currentChild
            // -- and explicitly saving our position counter (number of nodes
            // yielded so far).
            //
            // %REVIEW% Should position also be saved by setMark()?
            // (It wasn't in the XSLTC version, but I don't understand why not.)

            final int temp = _position; // Save state
            setMark();

            reset();            // Count the nodes found by this iterator
            do {
                _last++;
            }
            while (next() != END);

            gotoMark();        // Restore saved state
            _position = temp;
        }

        return _last;
    }

    /**
     * @return The position of the current node within the set, as defined by
     * XPath. Note that this is one-based, not zero-based.
     */
    public int getPosition() {
        return _position == 0 ? 1 : _position;
    }

    /**
     * @return true if this iterator has a reversed axis, else false
     */
    public boolean isReverse() {
        return false;
    }

    /**
     * Returns a deep copy of this iterator. Cloned iterators may not be
     * restartable. The iterator being cloned may or may not become
     * non-restartable as a side effect of this operation.
     *
     * @return a deep copy of this iterator.
     */
    public DTMAxisIterator cloneIterator() {

        try {
            final DTMAxisIteratorBase clone = (DTMAxisIteratorBase) super.clone();

            clone._isRestartable = false;

            // return clone.reset();
            return clone;
        } catch (CloneNotSupportedException e) {
            throw new wx.xml.xalan.xml.utils.WrappedRuntimeException(e);
        }
    }

    /**
     * Do any final cleanup that is required before returning the node that was
     * passed in, and then return it. The intended use is
     * <br />
     * <code>return returnNode(node);</code>
     * <p>
     * %REVIEW% If we're calling it purely for side effects, should we really
     * be bothering with a return value? Something like
     * <br />
     * <code> accept(node); return node; </code>
     * <br />
     * would probably optimize just about as well and avoid questions
     * about whether what's returned could ever be different from what's
     * passed in.
     *
     * @param node Node handle which iteration is about to yield.
     * @return The node handle passed in.
     */
    protected final int returnNode(final int node) {
        _position++;

        return node;
    }

    /**
     * Reset the position to zero. NOTE that this does not change the iteration
     * state, only the position number associated with that state.
     * <p>
     * %REVIEW% Document when this would be used?
     *
     * @return This instance.
     */
    protected final DTMAxisIterator resetPosition() {

        _position = 0;

        return this;
    }

    /**
     * Returns true if all the nodes in the iteration well be returned in document
     * order.
     *
     * @return true as a default.
     */
    public boolean isDocOrdered() {
        return true;
    }

    /**
     * Returns the axis being iterated, if it is known.
     *
     * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple
     * types.
     */
    public int getAxis() {
        return -1;
    }

    public void setRestartable(boolean isRestartable) {
        _isRestartable = isRestartable;
    }

    /**
     * Return the node at the given position.
     *
     * @param position The position
     * @return The node at the given position.
     */
    public int getNodeByPosition(int position) {
        if (position > 0) {
            final int pos = isReverse() ? getLast() - position + 1
                                        : position;
            int node;
            while ((node = next()) != DTMAxisIterator.END) {
                if (pos == getPosition()) {
                    return node;
                }
            }
        }
        return END;
    }

}
